Coordinate measuring machine and a method for correcting non-linearities of the interferometers of a coordinate measuring machine

Abstract

A method and a coordinate measuring machine ( 1 ) are provided, wherein the non-linearities of an interferometer ( 24 ) can be corrected. A measuring stage ( 20 ) traversable in a plane ( 25 a ) is provided for measurement. The substrate ( 2 ) is placed in a measuring stage ( 20 ); wherein the position of the measuring stage ( 20 ) along each of the motion axes is determined by at least one interferometer ( 24 ) in each case. A computer ( 16 ) is provided for compensating the non-linearity inherent in each of the interferometers ( 24 ), wherein the position of the measuring stage ( 20 ) to be determined by the interferometers ( 24 ) is arranged along a trajectory ( 52, 60, 67 ) of the measuring stage ( 20 ), which is composed at least partially of components of the axes.

1. A machine for determining position of structures on a substrate, comprising:
 a measuring stage traversable in a plane defined by an axis in a X coordinate direction and an axis in a Y coordinate direction; 
 a measuring lens arranged in an optical axis for determining position of the structures on the substrate; 
 a measuring stage, wherein a measuring position at which at least one structure to be measured is moved by the measuring stage relative to the optical axis and wherein the substrate is positioned on the measuring stage; 
 interferometers determining position of the measuring stage along each of the axes; and 
 a computer connected to each interferometer for determination of position of the measuring stage, wherein the computer corrects non-linearity of each interferometer by determining position of the measuring stage along a trajectory of the measuring stage using each interferometer, 
 wherein a part of the trajectory is directed toward a measuring position and another part of the trajectory is directed away from the measuring position; 
 wherein the trajectory approaching the measuring position at least partially comprises motion in the X direction and in the Y direction to obtain correction values applicable to the determining position of a structure on the substrate at the measuring position, and 
 wherein the measuring position is initially approached along the trajectory at a high velocity and then, before the measuring position is reached, at a reduced velocity to record and process data to correct the interferometer non-linearity using the computer. 
 
     
     
       2. The machine according to  claim 1 , further comprising an interferometer determining an angular position of the measuring lens relative to the optical axis. 
     
     
       3. The machine according to  claim 1 , further comprising interferometers are used for measuring position of the measuring stage and/or for measuring angular position of the measuring stage and/or the measuring lens and/or for measuring a reference wavelength. 
     
     
       4. The machine according to  claim 1 , further comprising an etalon with a variable length to determine correction values for the non-linearity correction. 
     
     
       5. The machine according to  claim 4 , further comprising a piezoelectric drive changing the length of the etalon. 
     
     
       6. A method for correcting non-linearities of interferometers of a coordinate measuring machine comprising the interferometers, a measuring stage traversable in a plane defined by an axis in X coordinate direction and an axis in Y coordinate direction, and a measuring lens in an optical axis for determining position of structures on a substrate placed on the measuring stage, wherein a measuring position of at least one structure is positioned at the optical axis by the measuring stage; the method comprising the steps of:
 recording position data for the measuring stage by the interferometers simultaneously moving the measuring stage toward the measuring position from one direction and/or moving the measuring stage away from the measuring position in another direction for determination of the position of the structure on the substrate, wherein one interferometer is associated with the movement of the measuring stage in each of the X coordinate direction and in the Y coordinate direction, respectively; 
 moving the measuring stage along a trajectory toward the measuring position and away from the measuring position, which is composed at least partially of movement in the X coordinate direction and in the Y coordinate direction; 
 using a computer to determine the non-linearity of the interferometers from at least a part of the position data for the measuring stage along the trajectory, and 
 compensating the non-linearity of the interferometers at each measuring position by the computer, and 
 wherein the measuring position is initially approached along the trajectory at a high velocity and then, before the measuring position is reached, at a reduced velocity to record and process data to correct the interferometer non-linearity using the computer. 
 
     
     
       7. The method according to  claim 6 , wherein the measuring stage is moved obliquely from one measuring position toward the next measuring position and the measuring stage is moved obliquely away from one measuring position to a next measuring position to collect correction data simultaneously in the X coordinate direction and Y coordinate direction. 
     
     
       8. The method according to  claim 7 , wherein the correction data is collected once during the movement toward the measuring position and/or during movement away from the measuring position, and the correction data is used for a plurality of measuring positions on the substrate. 
     
     
       9. The method according to  claim 6 , wherein the measuring position is only traversed in one axis direction, to obtain correction data in this direction only, wherein the correction data for the other direction is taken from data collected during the previous traversal in the other direction. 
     
     
       10. The method according to  claim 6 , further comprising obtaining correction values for the non-linearity correction using an etalon with a variable length. 
     
     
       11. The method according to  claim 10 , further comprising changing the length of the etalon with a piezoelectric drive.